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Compaq Portable restoration

tkc8800

Experienced Member
Joined
Jul 1, 2014
Messages
145
Location
Adelaide, South Australia
I saw this Compaq portable advertised in my local area, not knowing much about these machines I did a bit of research on it. I discovered that it was not only the first IBM pc clone but also Compaq's first product from the early 80's. I really like these old "portables" with built in CRT's so I snapped it up. The price was fairly cheap, so I bought it without doing much testing. The seller didn't have any working boot disks, so I just tested that it powered up and displayed a missing boot disk prompt on the screen, that was good enough for what I paid.

On getting it home and doing some initial testing, I was happy to get it to boot from the A drive with a DOS 3.3 boot disk, but on the down side, I couldn't get any of the keys on the keyboard to respond. No really being able to do much more at that stage I pulled it apart and and gave it a full clean out. On pulling apart the keyboard I discovered that is uses these capacitive key pads under the keys to make contact with the circuit board. I've never seen these before, but did a bit of reading and found out they are used on several other models like the Sol20 and Apple Lisa. It was pretty clear to see why none of the keys were working as both the sponge material and the Mylar on the key pads had totally perished (see photo below). I read a great guide on a Sol 20 website that suggested making your own pads using sponge discs topped with aluminum foil and clear plastic tape. I didn't have any sponge material on hand so I just used some padded double sided tape instead. I create a test key and tested it on the keyboard pcb and all keys worked. I then proceeded to make similar pads for all keys on the keyboard. This took a couple of hours but once re-assembled, I had a fully working keyboard. The keyboard fix was good as I can now use the machine, but I'm not happy with the feel of the keys. The double sided tape that I used does have some spring to it, but it's way too hard compared to the sponge material. So at some stage I'll redo the pads using a more appropriate material.

With a working keyboard I did some further testing on the machine and found that the B drive didn't read any disks. I pulled it out and cleaned it internally and also did a thorough head clean, on re-installing the B drive it now reads some disks, but it's not perfect. I've noticed it gets to a certain track on the disk and then comes up with read errors. I'll need to extract that drive again and check the rails for debris. I can launch some programs from that drive now so it's better than before. Everything else on the machine seems to work well, the display is good, there's some geometry issues, but the green screen display is very sharp and there's no sign of any burn in. The machine has the floppy printer card installed and also has an AST SixPakPlus clock/memory/serial upgrade card installed. Memory reports at 640k, I also replaced the 3v battery on the AST card and I found the AST clock utilities on web, the clock now saves the date and time.

After a thorough clean the case came up really well, no cracks or visible damage, so cosmetically it's really nice.

If anyone out there has the original disk images for the Compaq DOS v1 or v2, or any other resources or manuals for this machine, I would love to get a copy of those.


Case prior to cleaning:
cp1.JPG


cp2.JPG


The perished capacitive key pads:
cp4.JPG


Testing the keyboard with the pcb:
cp5.JPG


Here's what was left of the keypad foam:
cp6.JPG


My home made capacitive key pads:
cp7.0.JPG


Working keyboard:
cp7.1.JPG


Top view with cards removed:
cp8.JPG


Working machine after clean out and keyboard fix:
cp9.JPG


cp10.JPG


The floppy/printer board:
IMG_1461.JPG


The full size video board:
IMG_1462.JPG


The AST SixPakPlus
IMG_1463.JPG
 

reenigne

Veteran Member
Joined
Dec 13, 2008
Messages
707
Location
Cornwall, UK
That video card is fascinating - I had no idea there was such a thing as a hybrid CGA/MDA card with composite output. Nice teardown - thanks!
 

tkc8800

Experienced Member
Joined
Jul 1, 2014
Messages
145
Location
Adelaide, South Australia
That video card is fascinating - I had no idea there was such a thing as a hybrid CGA/MDA card with composite output. Nice teardown - thanks!

Yeah, the video card is impressive, it's a massive thing. Pretty well thought out, there's an internal cable that connects to the top for the in-built mono screen.
 
Last edited:

motley2659

Member
Joined
Feb 19, 2013
Messages
48
Ugh @ foam and foil key switches. Such a great looking computer with such a mushy keyboard.
 

tkc8800

Experienced Member
Joined
Jul 1, 2014
Messages
145
Location
Adelaide, South Australia
Ugh @ foam and foil key switches. Such a great looking computer with such a mushy keyboard.

I'm not happy with it either, it's a temporary fix, it beats no keyboard. As soon as I can source some appropriate replacement foam pads, I'll re-do it. The fix I did is fully reversible so no problems there.
 
Last edited:

tkc8800

Experienced Member
Joined
Jul 1, 2014
Messages
145
Location
Adelaide, South Australia

reenigne

Veteran Member
Joined
Dec 13, 2008
Messages
707
Location
Cornwall, UK
I don't think that is MDA, i believe it is some kind of modified CGA with a special tube, that will emulate colors in different shades of green. I might be wrong, a second opinion?

The pictures definitely look like MDA, and wikipedia says "The machine used a unique hybrid of the IBM MDA and CGA which supported the latter's graphics modes, but contained both cards' text fonts in ROM."
 

motley2659

Member
Joined
Feb 19, 2013
Messages
48
The IBM Portable 5155 is CGA but run through a composite amber display, like a mini Amdek 300A. I may be wrong, but the Compaq looks like a green phosphor version of that.
 

sergey

Veteran Member
Joined
Jul 15, 2010
Messages
732
Location
Silicon Forest, Oregon, USA
Great job!
I also have a Compaq Portable. And just as in your case the keyboard pads deteriorated. So I need to find time and materials to fix the keyboard.
I tried using double sided adhesive tape + aluminum foil + transparent scotch tape, but it doesn't work as good as original foam pads. So I am still looking for a better solution.
 

lee4hmz

Experienced Member
Joined
Sep 28, 2013
Messages
90
Location
Woodbridge, VA
The pictures definitely look like MDA, and wikipedia says "The machine used a unique hybrid of the IBM MDA and CGA which supported the latter's graphics modes, but contained both cards' text fonts in ROM."

I went looking for an official Compaq manual, and I found one on minuszerodegrees. It says that the hi-res text mode is indeed 720x350 (which is good, because I thought it was 640x400 myself).
 

PhilipA

Experienced Member
Joined
Aug 4, 2013
Messages
470
Location
Larose, LA, USA
Great job!
I also have a Compaq Portable. And just as in your case the keyboard pads deteriorated. So I need to find time and materials to fix the keyboard.
I tried using double sided adhesive tape + aluminum foil + transparent scotch tape, but it doesn't work as good as original foam pads. So I am still looking for a better solution.

Mylar emergency blanket from on outdoor sports store (think Academy sports), I used contact adhesive on a thick high-density foam sheet I bought at a craft store. Applied the adhesive, made sure with a meter the conductive side of the Mylar was being glued, then punched out with a home-made punch (sharpened pipe) and stuck to the original plastic backing circles that were still stuck in the keys.

--Phil
 

gnelec

New Member
Joined
Mar 19, 2015
Messages
1
I don't know weather you guys can direct me to the right forum but I have a Compaq SLT/286 Portable with expansion base! Rare I know! Ive installed 2 ISA cards to the base, a future domain SCSI card & a SoundBlaster 16 card & for some uknown reason the system wont detect them. Ive tried playing around with the I/O, IRQ, DMA etc still no joy. its like the SLT thinks that the ISA bus doesn't exist. Have any of you guys had any issues with this? or know where to get info on how to set up the expansion base properly & ISA setups?
 
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